The present invention relates to an electrical switch for controlling the operation of an electrical appliance.
The temperature of electrical switches rises during operation. Heat is generated by electrical current flowing, through the switch contacts and by the making and breaking switch contact. Overheating of electrical switches, within the limitation of size, has always been a problem.
The invention seeks to mitigate or at least alleviate the problem by providing an electrical switch that has an improved heat dissipation capability.
According to the invention, there is provided an electrical switch comprising a body, a plurality of control terminals and a common terminal supported by the body for external connection, and a movable contact provided within the body for establishing connection between the control terminals and the common terminal. The movable contact has one part connected to the common terminal and a plurality of other parts movable to connect to the control terminals respectively. Each of the other parts is movable between a first position in contact with the corresponding control terminal and a second position separated from the corresponding control terminal. A switching member is supported by the body for moving the other parts of the movable contact to establish the connection. A common metal heat sink is located within the body for contact by the other parts of the movable contact when the other parts are in the second positions.
It is preferred that the other parts of the movable contact are resiliently biased towards their first positions.
Preferably, the body has a pair of opposite ends at which the control terminals and the common terminal are located respectively, and the movable contact extends across the control terminals and the common terminal.
More preferably, the movable contact has opposite first and second ends, with the first end acting as the one part and the second end divided into prongs acting as the other part, respectively.
Further, more preferably, the prongs are resiliently pivotable about the first end of the movable contact.
For example, the switching member is supported by the body for sliding movement.
The heat sink may comprise a metal plate.
In a preferred embodiment, the body has a defined space for receiving the heat sink, and the heat sink has a size substantially the same as that of the space for its location.
Preferably, the body comprises first and second parts, the first part including an abutment facing the second part, and the heat sink is provided within the second part and held in position by the abutment.
More preferably, the abutment extends at a position between the control terminals for flashover protection.
The invention also provides a hairdryer incorporating the electrical switch, comprising an electric motor and an electrical heating element connected to the control terminals, respectively.